Technology: Coaxial speakers
Keb’Mo’ (left) with brother and sister four-piece L’Angélus at the launch of the Active Integration (AI) series at NAMM 2013
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Dual in the crown
How do coaxial loudspeaker designs fit into today’s live sound inventories? Phil Ward investigates the spate of recent interest in the technology
AS COMEBACKS go, it’s not quite The Rolling Stones. But coaxial speaker designs are back on the agenda this year, even if – like Jagger & Co – they never really went away. The question facing them now is whether they can, as some protagonists are claiming, satisfy the awkward needs of a large number of people lolling about a venue and gawping at the stage. “I take a very pragmatic
approach,” says FOH engineer Jon Burton. “I’m a big fan of coaxial speakers, owning several Tannoy Dual Concentrics, but for the type of gigs I do they don’t fit. Point source is great, but how do you make a big enough coaxial speaker to cover the size of audience you need to? If I had my way, I’d have coaxial six-deep with a 31” in the middle, a 15 in the centre of that and a 2 in the centre of that… all sat in the middle of the stage! But it’s just not practical. “We still use the d&b C4 for The Prodigy, which is a 15 and a
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“Without doubt, VQ Live has outperformed any systems I have used before. It’s probably the best point source box I have ever used in my career” Andy Linklater, FOH engineer
2” coaxial. I took it out on tour as soon as it appeared in the ’90s, but the trouble is that once you build a stack you no longer have a single point source. Put two together and you have two point sources: you’ve lost all the benefits and reintroduced cone filtering and all the other associated problems. You’ll always get wider dispersion on the lows than the mids. The best small-venue systems I’ve heard have been compact line arrays – even brands I’ve never heard of.”
“Fundamentally, all
frequencies come from a notional centre: so coax is point source at its purest,” agrees Funktion One’s Tony Andrews. “But if you’ve two things alongside each other, any movement from the sweet spot ruins everything because the arrival of the two sources alters. That’s why coax is so popular in wedge monitors – they don’t do that. You can scale them up to an extent – we’ve done one with an 18 that Carl Cox uses, for example, as
COAXIAL: THE JOURNEY
From studio monitors to monitoring wedges, and now to FOH: the coaxial has been around for a very long time, but only latterly has it been embraced as a portable option for the reinforcement of an entire room. Altec Lansing introduced the 601 Duplex for recording studios as far back as 1943, and its successor the 604 dominated the US scene for many years. In Europe, Tannoy responded with the Dual Concentric in 1947, but both suffered from a lack of time alignment between the concentric drivers and SPL- induced intermodulation distortion as the low and high frequencies mingled in the same axis.
These and other problems were tackled by Bill Puttnam and Ed Long in the ‘70s, leading to the UREI 813’s patented Time Alignment crossover. On stage, the compactness of single- point source designs – together with the even field of acoustic radiation – made them popular for wedge monitors among several brands from Clair Bros to Radian, but a new generation is emerging that attempts to apply exactly this stability to FOH applications. To date, the scale of these systems remains small, and the market faces increased competition from ever- more compact line arrays.
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